Hydrostatically balanced bumper sub



March 28, 1967 L. E. GILREATH ETAL 3,311,180

HYDROSTATICALLY BALANCED BUMPER SUB Filed March 30, 1964 2 Sheets-Sheetl United States Patent 3 311 180 HYnRosTATrcALLYBAiANcEn BUMPER SUBLafayette E. Giireath and Eddie C. McGarrahan, Houston, Tex., assignorsto Houston Oil Field Material Company, Inc., Houston, Tex., acorporation of Delaware Filed Mar. 30, 1964, Ser. No. 355,836 9 Claims.(Cl. 175-293) The present invention relates to a hydrostaticallybalanced bumper sub, and more particularly, relates to a bumper sub foruse in a drilling string for drilling a well bore in which the sub, whenconnected in the drill string, and subjected to the high pressure fluidsboth in the drilling string and in the well bore provides a structure inwhich the vertical hydrostatic forces acting on the sub are balanced.

Generally, a bumper sub is a tool which is connected in the drillingstring which is used to drill a well bore. A drilling type bumper sub isgenerally placed immediately above the drill bit or drill collars. Thebumper sub is used to affect a bumping action to prevent the drillstring from becoming stuck in the well bore. However, since the usualdrilling fluids are pumped down the drill string, out the drilling bit,and up the annulus between the drilling string and well bore the bumpersub will be subjected to the usual hydrostatic pressures of the fluid inthe string and in the well bore. Because of the great depths to whichwells are now being drilled, these hydrostatic pressures areconsiderable and act against any unbalanced areas of the surfaces of thedrilling string including the bumper sub and create tremendous forceswhich may adversely affect the drilling operation. For instance, it isdesirable in drilling operations to keep the drill string as straight aspossible so as to drill straight holes and to accomplish this result thedrill string is generally kept in tension. Therefore, if the bumper subprovides a downwardly directed horizontal surface area in excess of thearea of its upwardly directed horizontal surfaces, an upwardly directedhydrostatic force may result, particularly in deep wells, which will acton and place the drilling string in compression and cause it to bow orcork screw. Furthermore, unbalanced hydrostatic forces may act on themovable or bumper section of the bumper sub and cause the sub to belocked in position and prevent its operation.

Therefore, it is a general object of the present invention to provide abumper sub in which all of the vertical hydrostatic forces acting on thebumper sub are balanced.

A still further object of the present invention is the provision of abumper sub having a housing, a wash pipe connected thereto, and atelescoping supporting stem connected to the lower end of the drillstring in which the areas of the horizontally directed surfaces on thehousing and wash pipe which are exposed to the well fluid are balancedto prevent any vertical hydrostatic pressure acting on the drill string.

Yet a further object of the present invention is the provision of abumper sub having the usual housing and wash pipe for connection at itsupper end in a drill string, and a telescoping supporting stem which isadapted to support the lower portion of the drill string in which theexposed horizontal areas of the housing and wash pipe are substantiallyequal, and the hydrostatic pressure acting in an upward direction on thesupporting stem is balanced or overcome by adding drill collars having asuflicient weight to the lower end of the stem.

Yet a still further object of the present invention is the provision ofa hydrostatically balanced bumper sub having a housing adapted to beconnected at its upper end to a drilling string, a wash pipe connectedto and forming an annulus with the housing, and a supporting stem the3,3l L Patented Mar. 28, 167

upper end of which telescopes into the annulus and is nonrotativerelative to the housing, and in which the annulus is sealed from thefluid in the drill string and well bore whereby the jarring and contactsurfaces are enclosed in a suitable lubricant.

A still further object of the present invention is the provision of ahydrostatically balanced bumper sub having a housing, a wash pipe, atsupporting stern telescoping in an annulus between the wash pipe andhousing and sealin ly engaging the wash pipe and annulus and wherein anannular lubricant divider is connected to the top end of the stem toinsure adequate lubrication on the engaging surfaces and whereinbearings having spiral helical grooves are provided to cause thehearings to rotate and prevent grooving of the bearing surfaces.

Yet a further object of the present invention is the provision of ahydrostatically balanced bumper sub having a housing and a wash pipeforming an annulus, a supporting stem, the upper end of which istelescopically slidable in said annulus, said annulus including a gasand a lubricant, but sealing the upper end of said stem from hydrostaticforces and in which the horizontal surfaces of the housing and washpipe, when the sub is positioned in a drilling string, are balanced.

Other and further objects, features and advantages will be apparent fromthe following description of a presently preferred embodiment of theinvention, given for the purpose of disclosure and taken in conjunctionwith the accompanying drawings, where like character referencesdesignate like parts throughout the several views, and where,

FIGURE 1A is a fragmentary elevational view, partly in cross-section,illustrating the top portion of the bumper sub of the present invention,

FIGURE 2 is an enlarged cross-sectional view taken along the line Z2 ofFIGURE 1A,

FIGURE 3 is an enlarged cross-sectional view taken along the line 33 ofFIGURE 1A,

FIGURE 13 is a fragmentary elevational view, partly in cross-section,and is a continuation of FIGURE 1A,

FIGURE 1C is a fragmentary elevational view, partly in cross-section,and is a continuation of FIGURE 1B, and

FIGURE 4 is an enlarged perspective view of one of the spirally groovedbearings of the present invention.

Referring now to the drawings, the reference numeral 10 generallyindicates the hydrostatically balanced bumper sub of the presentinvention and generally includes a housing 12 and a wash pipe 14 whichare connected together and adapted to be connected at their upper endsto the upper portion 15 of a conventional drill string, and includes asupporting stem 16 which slidably telescopes within the housing 12 andat its lower end (FIG- URE 1C) is adapted to be connected to and supportthe lower portion 18 of the drilling string.

The housing 12 may include, as best seen from FIG- URE 1A, an upper sub20 having conventional threads 21 for connection to the upper portion 15of the drill string, and as best seen in FIGURES 1B and 1C,respectively, upper cylinder 22 and lower cylinder 24. And between theupper and lower cylinders a hexagonal guide sub 26 is provided, which aswill be more fully described hereinafter engages the hexagonal portion32 of the supporting stem 16 to provide rotative movement between thehousing 12 and the stem 15.

Referring again to FIGURE 1A, the wash pipe 14 is secured such as bythreads to upper sub 24} and in addition to serving to direct the drillstring fluid downwardly through the Wash pipe is spaced from the uppercylinder 22 to provide an annulus 30 in which the upper end of thesupporting stem 16 moves.

The supporting stem 16 slidingly telescopes with the upper and lowercylinders 22 and 24 as best seen in FIG- URES 1A and 1B and as best seenin FIGURE 3 includes a hexagonal section 32 for engagement with thehexagonal sub 26 (FIGURE 1B) whereby rotative movement may betransmitted from the housing 12 to the supporting stem 16 and thus .tothe lower portion of the drilling string 18 (FIGURE 1C). Furthermore,the supporting stem 16 includes upper engaging shoulder 34 (FIGURE 1A)and lower engaging shoulder 36 (FIGURE 1B) which on upward or downwardmovement of the housing 12 and of the hexagonal sub 26 will cause a bumpor jar against the shoulders 34 and 36 to provide a conventional bumpingaction to the lower portion 18 of the drilling string as may be desired.

However, as has previously been mentioned, in the present day practiceof drilling deep oil and gas wells the fluid pressures encountered inthe drill string and well bore have become increasingly large. Forexample in a 10,000 foot well the normal drilling pressure may be ashigh as 6,000 pounds per square inch. Therefore, it becomes important toinsure that any horizontally disposed surfaces on the well string whichare exposed to Well fluids are suitably compensated or balanced;otherwise tremendous forces will act against those surfaces with adverseresults. And, of course, if the movable stem 16 and the lower portion 18of the drill string are unbalanced the supporting stem 16 could becomelocked in position and thus be inoperable.

Therefore, it is important that all of vertical hydrostatic forces onthe bumper sub be balanced. Referring now to FIGURE 1A, it is noted thatthe outside diameter of the upper portion of the drill string has adiameter of A. And referring to FIGURE 1C it is to be noted that theinternal diameter of the cylinder 24 is also equal to A. Since theoutside areas or outside diameter of the housing 12, that is, sub 20,cylinders 22 and 24, and sub 26, are the same, it is therefore apparentthat the horizontally disposed surfaces on the housing 12 which areexposed to the drilling fluid, when the housing 12 is in position in thedrilling string, are equal in an upward and downward direction andtherefore the vertical hydrostatic forces on the outside of the housing12 are equal and thus balanced. That is, the upwardly directedhorizontal component of the surface 40 isequal to the downwardlydirected horizontal component of surface 42. Similarly, and referring towash pipe 14 the upwardly directed horizontal component of exposedsurface 44 (FIGURE 1A) is balanced by the downwardly directed horizontalcomponent of the surface 46 (FIGURE 1B). Therefore, the

hydrostatic forces acting on the housing 12 and the wash pipe 14 arebalanced and thus will not adversely affect the upper portion 15 of thedrilling string to which they are connected.

Referring again to FIGURE 1A it is to be noted that the annulus 30between the housing 12 and the wash pipe 14 includes a plug 48 throughwhich a suitable lubricant may be inserted for lubricating the engagingsurfaces between the movable supporting stem 16 and the housing 12, andthe wash pipe 14. Suitable seals 50 and 52 are provided between the stem16 and the wash pipe 14. Similarly, suitable seals 54 and 56 areprovided between the stem 16 and the housing 12 (FIGURE 1B). Thus, it isto be noted that the annulus 30 is sealed and is not exposed tohydrostatic pressures from the fluid in the drilling string and wellbore. Because of this, there will be no hydrostatic force acting againstthe upper end of the movable stem 16. Referring again to FIGURE 1A, thelubricant is filled through the plug 48 to a level 58 when the apparatus10 is in an extended position. This leaves the remainder of the annulus30 filled with air at atmospheric pressure of 14.7 pounds per squareinch. The volumetric change of air may be, for example, in the ratio ofthree to one so that the maximum air pressure in the annulus 30 when thebumper sub is fully closed will be less than 45 pounds per square inch.Thus, after the movable stem 16 is moved upwardly in the annulus 30,there will be an unbalanced pressure of 45 pounds per square inch actingdownwardly on the upper end of the stem 16, and upwardly on the uppersub 20. However, this pressure is insignificant in comparison with theother forces acting on the sub 10 and will have no adverse effects onthe drill string or on the operation of the sub 10. Nevertheless, theuse of a gas in the closed and sealed annulus 30 prevents the presenceof well fluids and their extremely high pressures and adverseconsequences, and yet does not provide a hydraulic block as would be thecase if the entire annulus were filled with lubricant.

Referring now to FIGURES 1A, 1B, and 1C, it is to be noted that theexposed horizontal components of the downwardly directed faces of .themovable stem 16 are not balanced by the horizontal components of anyupwardly directed faces on the movable stem which are exposed to thetremendous hydrostatic pressures in the well bore. This is because theupper end of the movable stem 16 is positioned in the annulus 30 andsealedoff from the hydrostatic pressures in the well bore by the seals50 and 54. Thus, an upwardiforce acts on t-he'stem 16 having antagnitudeof the hydrostatic pressure. times the cross sectional area between the,outer diameter of the washpipe 14 and the inner diameter of theupper andlower cylinders 22 and 24. Therefore, suitable drill collars (not shown)must be connected to the lower portion 18 of the drill string with asufficient weight to balance the upwardly directed hydrostatic pressuresacting on the movable stem 16.

Referring now to FIGURES lA and.2, it is to be noted that an annularlubricant divider 68' is provided connected to the upper end of the stem16 sothat lubricant will remain in 'a cup 7 0. regardless of theposition of the stem 16 relative to the housing 12 so as to providesuflicient lubrication for the contact surfaces between the. wash pipe14 and the stem 16. Otherwise, if the lubricant level falls below thetop of the stem. 16, only the surfaces between the stem 16 and thehousing 12 would be lubricated.

And referring to FIGURES 1A and 1B, suitable bearings. 72 are providedabout the movable stem 16 andengaging the upper and lower cylinders 22and 24. Referring to FIGURE 4 it is noted that the bearings 72 includespiraling grooves74 which will cause the bearing 72 to rotate andprevent grooving of the bearing surfaces.

In operation, the bumper sub 10 of the present invention is connectedinto a conventional drilling string. In the case of using the bumpersubas a drilling-type bumper sub, it is run immediately above the bit ordrill collars (not shown). Since the housing 12' is threadably connectedto the upper portion of the drill string 15v (FIG- URE 1A), the rotativemovement of the drill string will be transmitted by hexagonal sub 26through hexagonal surfaces 32 on the telescoping stem. 16 to the lowerportion of the drilling string 18 (FIGURE 1C) and to the drill hit. Asis convention the bumper sub may provide a bumping or jarring-action. 15of the drill stn'ng may be raisedand lowered thereby raising andlowering the hexagonal sub-26 to alternately contact or jar engagingshoulders34 and 36 on the sup porting stem 16. to alternately jar thelower portion 18 of the drilling string upwardly and downwardly.However, it is to be noted that the areas of the horizontally directedsurfaces on the housing 12 and the wash pipe 14, which are exposed towell fluids, are balanced in an upward and downward direction. That is,the areas directed upwardly are substantially equal to the areas di--rected downwardly thereby balancing the vertical hydrostatic pressuresacting on these elements. The unbalanced upwardly directed force actingon the supporting stem 16 is balanced by the weight of drill collars(not shown) connected tothe lower portion of the drilling string 18. Itis to be noted that the upper end of the supporting stem 16 ispositioned in the annulus 30 (FIG- That is, the upper portion- URE 1A)between the housing 12 and the wash pipe 14 and thus is not subjected toany hydrostatic pressures in the well bore. As previously mentioned, theair in the annulus 38 may vary for example from 14.7 pounds per squareinch to approximately 45 pounds per square inch as the jar is operatedbut this will not be sufiicient to cause any adverse effects on thedrilling string or bumper sub ill.

The present invention, therefore, is well suited and adapted to attainthe ends and objects mentioned herein as well as others inherenttherein. While a presently preferred embodiment of the invention isgiven for the purpose of disclosure numerous changes in the details ofconstruction and arrangement of parts may be made which are within thespirit of the invention and the scope of the appended claims.

What is claimed is:

1. A hydrostatically balanced bumper sub for use in a drilling stringcomprising,

a housing adapted to be connected in the drilling string,

a washpipe connected to and positioned inside of the housing,

a supporting stern telescoping in and nonrotatably engaging the housingand the lower end of which is adapted to be connected in the drillingstring,

the horizontally disposed surfaces of said housing, and wash pipe, whenthe sub is connected in a drilling string, and which are exposed tohydrostatic pressures inside and outside of the drilling string, havingareas which are substantially equal in an upward and a downwarddirection whereby the forces generated by the pressures acting thereonwould be substantially balanced.

2. The invention or" claim 1 wherein,

the horizontally disposed upwardly and downwardly directed surfaces onsaid wash pipe have areas which are substantially equal, and

the horizontally disposed upwardly and downwardly directed surfaces onthe housing have areas which are substantially equal.

3. A hydrostatically balanced bumper sub for use in a drilling string ina well bore comprising,

a housing adapted to be connected at its upper end to the drillingstring,

a wash pipe connected to and positioned inside of and forming an annuluswith said housing, said annulus being sealed from the well bore andincluding a gas,

a supporting stem, the upper end of which telescopes in said annulus andnon-rotatably engages said housing, and the lower end of which isadapted to be connected in the drilling string, and

the upwardly and downwardly directed horizontally disposed surface areasof the housing and wash pipe, when the sub is positioned in a drillingstring, are substantially equal, thereby balancing the verticalhydrostatic forces on said housing.

A hydrostatically balanced bumper sub for use in a drilling string in awell bore comprising,

a housing adapted to be connected at its upper end in the drillingstring,

a wash pipe connected to and positioned inside of and forming an annuluswith said housing,

a supporting stem, the upper end of which telescopes in said annulus andnon-rotatably engages said housing, and the lower end of which isadapted to support a lower portion of the drill string,

said annulus being sealed from fluids in the well bore and including agas,

the upwardly and downwardly directed horizontally disposed surfaces ofthe housing and the wash pipe, when the bumper sub is positioned in adrilling string, having areas which are substantially equal whereby theforces generated by the ressures acting thereon would be substantiallybalanced.

5. The invention of claim 4 including,

a weight connected to the lower end of the supporting stern sufiicientto balance the upwardly directed hydrostatic force acting on thesupporting stem.

6. A hydrostatically balanced bumper sub for use in a drilling string ina well bore comprising,

a housing adapted to be connected at its upper end in the drillingstring,

a wash pipe connected to and positioned inside of and forming an annuluswith said housing,

a supporting stem, the upper end of which telescopes in said annulus andis nonrotative relative to said housing, and the lower end of which isadapted to be connected in the drilling string,

sealing means between the supporting stem and said housing,

sealing means between said supporting stem and said wash pipe,

said annulus being sealed from the well fluid in a drilling string andwell bore,

gaseous means in said annulus,

a scalable opening in said annulus for supplying lubricating oil to thetelescopically engaging surfaces between the supporting stern and saidhousing and wash pipe,

hammer engaging surfaces on said supporting stern and housing forsupplying a jar when engaged, and

the upwardly and downwardly directed horizontally disposed surfaces ofthe housing and wash pipe, when positioned in a drilling string, havingareas which are substantially equal whereby the forces generated by thepressures acting thereon would be substantially balanced.

7. The invention of claim 6 including,

annular bearings between the supporting stern and said housing,

the face of said bearings including helically spiraling grooves.

3. The invention of claim 6 including,

an annular lubricant divider connected to the upper end of saidsupporting stem to supply lubricant on both sides of said supportingstem.

9. The invention of claim 6 including,

a weight connected to the lower end of the supporting stein suflicientto counterbalance the hydrostatic upwardly directed force created by thewell bore pressures acting on the downwardly directed surfaces of thesupporting stern.

References Cited by the Examiner J. A. LEPPINK, Assistant Examiner.

1. A HYDROSTATICALLY BALANCED BUMPER SUB FOR USE IN A DRILLING STRINGCOMPRISING, A HOUSING ADAPTED TO BE CONNECTED IN THE DRILLING STRING, AWASHPIPE CONNECTED TO AND POSITIONED INSIDE OF THE HOUSING, A SUPPORTINGSTEM TELESCOPING IN AND NONROTATABLY ENGAGING THE HOUSING AND THE LOWEREND OF WHICH IS ADAPTED TO BE CONNECTED IN THE DRILLING STRING, THEHORIZONTALLY DISPOSED SURFACES OF SAID HOUSING, AND WASH PIPE, WHEN THESUB IS CONNECTED IN A DRILLING STRING, AND WHICH ARE EXPOSED TOHYDROSTATIC PRESSURES INSIDE AND OUTSIDE OF THE DRILLING STRING, HAVINGAREAS WHICH ARE SUBSTANTIALLY EQUAL IN AN UPWARD